Field of the Invention
The present invention relates to a wrapped bush joined at ends thereof and, more particularly, to a wrapped bush in which the ends to be joined at the joint of the bush are formed with joint portions which each have at least one pair consisting of a recess and a projection and which are of the same configuration and of the same size but are shifted in the axial direction of the bush in such a manner that one joint portion of one end is disposed in supplementary relationship with the other joint portion of the other end, the bush thus being adapted to prevent the joint at which the ends are joined from expanding widthwise.
There are two types of joints of known wrapped bushes: the butt type joint (see FIG. 12) and the fastened type joint (i.e., the clinch type joint, see FIGS. 8 to 11). These two types are used in accordance with the purpose. The butt type joint, which involves no fastening force at the joint, is generally used from the viewpoint of economic efficiency, whereas the fastened type joint, which involves fastening force at the joint, is used when required by the function. A known wrapped bush of the fastened type usually has joint portions having at least one pair consisting of male and female portions of different configurations.
However, such a known wrapped bush of the fastened type, whose male and female portions at the joint portions have different configuration, tends to be unsatisfactorily formed, in particular, at its joint. This will be described in detail. As shown in FIGS. 8 to 11, a wrapped bush of this type may be either a wrapped bush 16a, 16b, or 16c, shown in FIGS. 8 to 10, in which the joint 7d, 7e, or 7f is formed by the engagement between a single pair consisting of male and female portions 18a, 18b, or 18c, that is, by the so-called single clinch; or a wrapped bush 17, shown in FIG. 11 in which the joint 7g is formed by the engagement between a plurality of pairs each consisting of male and female portions 19, that is, by the so-called complex clinch.
With each of the wrapped bush of the fastened type shown in FIGS. 8 to 11, in which the male and female portions of each pair have different configurations, although the ends of the bush can be joined by a large fastening (clinching) force, there is a difference in strength between the ends, particularly, in widthwise strength. Consequently, when the ends are joined, the bush expands widthwise, making it necessary to subject the bush to machining to cut off any expanded portion. Thus, the known wrapped bush of the above-described type fails to be properly formed, causing various problems such as an increase in production costs.